From fb653292612eddca5b088ed88466c546d1597107 Mon Sep 17 00:00:00 2001
From: Elizabeth Alexander Hunt <me@liz.coffee>
Date: Sat, 20 Jun 2026 09:40:07 -0700
Subject: Initial commit

---
 static/js/canvas.js | 97 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 97 insertions(+)
 create mode 100644 static/js/canvas.js

(limited to 'static/js/canvas.js')

diff --git a/static/js/canvas.js b/static/js/canvas.js
new file mode 100644
index 0000000..f164803
--- /dev/null
+++ b/static/js/canvas.js
@@ -0,0 +1,97 @@
+(function () {
+  const cfg = window.CANVAS;
+  const canvas = document.getElementById("canvas");
+  const ctx = canvas.getContext("2d");
+  canvas.style.width = cfg.cols * cfg.scale + "px";
+  canvas.style.height = cfg.rows * cfg.scale + "px";
+
+  // palette picker
+  let selected = 0;
+  const paletteEl = document.getElementById("palette");
+  cfg.palette.forEach((hex, i) => {
+    const sw = document.createElement("div");
+    sw.className = "swatch" + (i === 0 ? " selected" : "");
+    sw.style.background = hex;
+    sw.title = hex;
+    sw.addEventListener("click", () => {
+      selected = i;
+      [...paletteEl.children].forEach((c) => c.classList.remove("selected"));
+      sw.classList.add("selected");
+    });
+    paletteEl.appendChild(sw);
+  });
+
+  const hexFromInt = (c) => "#" + c.toString(16).padStart(6, "0");
+  const drawPixel = (x, y, hex) => {
+    ctx.fillStyle = hex;
+    ctx.fillRect(x, y, 1, 1);
+  };
+
+  // The server is authoritative: we only paint pixels it broadcasts back. Open
+  // the socket first and queue messages until the initial state is painted, so
+  // nothing placed during the load is lost.
+  let loaded = false;
+  const queue = [];
+  function apply(msg) {
+    if (msg.type === "place") drawPixel(msg.x, msg.y, hexFromInt(msg.c));
+    else if (msg.type === "cooldown") startCooldown(msg.ms);
+  }
+
+  let ws;
+  function connect() {
+    const proto = location.protocol === "https:" ? "wss" : "ws";
+    ws = new WebSocket(`${proto}://${location.host}/canvas/ws`);
+    ws.onmessage = (e) => {
+      const msg = JSON.parse(e.data);
+      loaded ? apply(msg) : queue.push(msg);
+    };
+    ws.onclose = () => setTimeout(connect, 1000);
+    ws.onerror = () => ws.close();
+  }
+  connect();
+
+  fetch("/canvas/state")
+    .then((r) => r.arrayBuffer())
+    .then((buf) => {
+      const bytes = new Uint8Array(buf);
+      const img = ctx.createImageData(cfg.cols, cfg.rows);
+      for (let p = 0; p < cfg.cols * cfg.rows; p++) {
+        img.data[p * 4] = bytes[p * 3];
+        img.data[p * 4 + 1] = bytes[p * 3 + 1];
+        img.data[p * 4 + 2] = bytes[p * 3 + 2];
+        img.data[p * 4 + 3] = 255;
+      }
+      ctx.putImageData(img, 0, 0);
+      loaded = true;
+      queue.forEach(apply);
+      queue.length = 0;
+    });
+
+  // cooldown indicator (server enforces; this is UI feedback)
+  let cooldownUntil = 0;
+  const cdEl = document.getElementById("cooldown");
+  function startCooldown(ms) {
+    cooldownUntil = Math.max(cooldownUntil, Date.now() + ms);
+    tick();
+  }
+  function tick() {
+    const rem = cooldownUntil - Date.now();
+    if (rem > 0) {
+      cdEl.textContent = `cooldown: ${(rem / 1000).toFixed(1)}s`;
+      requestAnimationFrame(tick);
+    } else {
+      cdEl.textContent = "";
+    }
+  }
+
+  canvas.addEventListener("click", (e) => {
+    if (Date.now() < cooldownUntil) return;
+    if (!ws || ws.readyState !== WebSocket.OPEN) return;
+    const rect = canvas.getBoundingClientRect();
+    const x = Math.floor(((e.clientX - rect.left) / rect.width) * cfg.cols);
+    const y = Math.floor(((e.clientY - rect.top) / rect.height) * cfg.rows);
+    if (x < 0 || x >= cfg.cols || y < 0 || y >= cfg.rows) return;
+    ws.send(JSON.stringify({ type: "place", x, y, i: selected }));
+    startCooldown(cfg.cooldownMs);
+  });
+})();
-- 
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